The Time-Honored Quest to Find the Rules of Time Travel

It’s 2077 in the city of Vancouver, now part of the North American Union, run by a “Corporate Congress.” Technically, everyone is still free and enjoys the fruits of a highly technologically advanced society—except they spend their lives paying down the massive debt owed to the corporations, and are subject to high surveillance in what amounts to a police state.

This is the fictional dystopian world of Continuum, a new series on SyFy now airing its second season. In the pilot, a band of guerilla freedom fighters called “Liber8” are sentenced to execution for blowing up a corporate headquarters, killing tens of thousands of people. But they escape via a time travel device, taking a law enforcement officer (“protector”) named Kiera with them, and all end up in 2012 by mistake—60 years earlier than they’d planned. [NOTE: mild spoilers below.]

Naturally, hijinks ensue. Liber8 seeks to change the future and thwart the eventual rise of the corporate conglomerate; Kiera wants to return to her husband and son, and hence wants the future to remain intact. She worms her way into the Vancouver Police Department as a special liaison, and teams up with a teenaged computer whiz named Alec, who will eventually grow up to become one of the corporate kingpins of the future (Bill Gates, Steve Jobs, and Warren Buffett rolled into one). His elder self may have even played a role in sending them all to 2012 in the first place.

Time travel is one of the most popular motifs in science fiction, for good reason: It plays into our penchant for “what if” scenarios, specifically those in which we can go back and correct past mistakes, thereby changing the future. But there are rules when it comes to time travel—or at least, there should be in a plausible fictional universe—and one such rule is there can be no paradoxes.

Technically, it shouldn’t be possible to change the past: as Lost phrased it in Season 5, “Whatever happened, happened.” But where’s the fun in that? Hence we get films like Back to the Future, where Marty McFly nearly keeps his parents from falling in love, thereby putting his very existence into question. The other possible option is a parallel universe or alternate timeline diverging into a separate chain of events while the original timeline remains intact—a key plot point in many movies, including Back to the Future 2:

Doc: Obviously, the time continuum has been disrupted creating this new temporal event sequence, resulting in this alternate reality.

Marty: English, Doc.

Doc: Let me illustrate. Imagine that this line represents time. 1985. The future. The past. Prior to this point in time, somewhere in the past, thetimeline skewed into this tangent, creating an alternate 1985. Alternate to you, me, and Einstein, but reality for everyone else.

Continuum has yet to take a firm stand either way—not because series creator Simon Barry hasn’t worked out the “rules” of his fictional universe, but because discovering those rules is the main thrust of the broader narrative arc, so he’s deliberately not showing his hand.

Early on, Alec explains to Kiera that either they are caught in a “time loop”—in which the presence of the time travelers has always been part of the sequence of events, and therefore the future cannot be changed—or the time travel has created a separate chain of events, an alternate timeline in which the future might turn out very different for everyone. Kiera and Liber8’s predicament is a real-time experiment in time travel, and we uncover pieces of evidence for each of these options along with them.

A time loop may sound like a silly device cooked up to add drama to a sci-fi series, but it’s actually an idea taken seriously by theoretical physicists, who know it by the more technical name “closed timelike curve.” Igor Novikov, a cosmologist at Copenhagen University Observatory, has compared time to a river that flows from the past into the future. Under general relativity, that river would speed up or slow down as it “flowed” through the universe. But a closed timelike curve essentially separates one small piece of time’s river from the main flow of events, like a whirlpool or eddy. It is mathematically possible to be always moving forward as you travel through time, and yet still end up right where you began.

If the presence of mass-energy were great enough (approaching infinity) in a particular area of space-time, it could conceivably become so warped that the elliptical path would come full circle and the two ends would meet, forming a closed loop. Time isn’t running backwards; it’s running in circles. In a true closed timelike curve, one can only continually relive the same sequence of events, not alter the past, and therefore one cannot change the future. (Sorry, fans of Groundhog Day!)

It is mathematically possible to be always moving forward as you travel through time, and yet still end up right where you began.

Stephen Hawking, for one, has objected to the theoretical possibility of closed timelike curves, not just because of the extraordinary energies required, but because such phenomena violate causality. There should be a “chronology protection conjecture,” in which the laws of physics conspire to prohibit time travel to the past—or at least make it highly unlikely—and hence avoid such troublesome paradoxes as accidentally killing one’s grandfather before one is born.

That particular threat is used both by Kiera and the members of Liber8 as they jockey for leverage in the brave new (or old) world in which they find themselves. Eventually, one character’s grandmother is, indeed, killed. But he doesn’t die, or vanish abruptly; nothing seems to change. This might be evidence for an alternate timeline scenario—or perhaps they really are all caught in a time loop and the grandmother wasn’t really his grandmother, or she’s not really dead. If Continuum aims to be logically consistent, those are the only options.

If it is true that the elder version of Alec orchestrated the journey through time in the first place, clearly he did so because deep down, he thinks he can alter the past. So far, Alec the Elder’s plan hasn’t changed at least one pivotal event: Despite her best efforts, despite knowing exactly when and where it was going to take place, Kiera fails to prevent a bomb detonation in central Vancouver that kills hundreds of people and marks the start of the revolution that eventually led to the rise of the Corporate Congress—at least in her original timeline. The fact that the bomb goes off (again) lends credence to the “Whatever happened, happened” model—the past cannot be changed.

Then again, perhaps some events, like the bombing, happen in more than one timeline. In a recent Season 2 episode, Kiera does appear to have thwarted a series of murders that occurred in her original timeline—unless this is another clever bit of misdirection. We’ll have to see how the rest of the series unfolds before we can conclude with any confidence just how time flows in the universe that Simon Barry created.

Jennifer Ouellette is a science writer and the author of The Calculus Diaries and the forthcoming Me, Myself and Why: Searching for the Science of Self. Follow her on Twitter @JenLucPiquant.